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TL431: Use as an adjustable clipper or limiter circuit

HSIN-CHE HSIEH
Prodigy 140 points
Part Number: TL431
Other Parts Discussed in Thread: LM431,

Tool/software:

The typical solution for building a clipper or limiter circuit is usually to use a Zener diode. However, Zener diodes are only available in certain voltages, and might not be very fast or ideal. Can I use the TL431 in place of a Zener diode to build an adjustable high-speed clipper or limiter?

I tried to simulate it as in the attached schematic. It seems to work very well, but I am worried that the simulation model might not accurately show the behavior under transients or high-frequency. I plan to run it at up to 500 kHz. Can it reliably operate at this frequency? My circuit does not need to handle negative voltage.

Thank you

  • 0
    TI__Intellectual 1400 points

    The TL431 will not perform well at those frequencies due to compensation capacitance the device has to achieve it's stability criteria. You may see the output begin to rise quickly, but then take much longer to reach the desired level. At high frequencies this will cause distortion in your output signal. See section 9.2.2.2.4 and figure 9-14 in the datasheet for a more detailed explanation.

    -Henry

  • 0 in reply to Henry Naguski
    Prodigy 140 points

    So, at lower frequency, TL431 can be used in clipping/clamping circuit, right? I see the datasheet mention clamping application.

    I later found that my circuit does not really need to handle hundreds of kilohertz.

    How would the variants of TL431 (e.g. LM431 or ATL431) behave in this application? Would any of them work better?

    Thank you

  • 0 in reply to HSIN-CHE HSIEH
    TI__Intellectual 1400 points

    The TL431 may be suitable for clamping depending on the exact frequency, but in general a different approach should be taken for high-frequency AC signals.

    TL431 is the same device as LM431, the only difference is in the name. ATL431 and the other similar devices will have very similar performance in this aspect, per their datasheets.

  • 0 in reply to Henry Naguski
    Prodigy 140 points

    I tested my circuit on a breadboard with a generic (not TI) TL431 I happen to have on hand. This is what I got. At 10 kHz, it looks good to me, but seems to be unusable at 100 kHz. I just found that working up to 10 kHz is good enough for me now.

    So TI branded TL431 or variants would not perform too differently, right? What are some proper ways to implement a clipper/clamper circuit if I want higher frequency later?

    Thank you

  • 0 in reply to HSIN-CHE HSIEH
    TI__Intellectual 1400 points

    While shunt references may have applications in clipper circuits, I do not have any additional design details or guidance for you. Please leverage published datasheets and application notes for detailed device comparison information.

  • 0 in reply to Henry Naguski
    Prodigy 140 points

    So, if I want to design a proper high-speed adjustable clipper circuit (without using TL431 or similar shunt reference), what should I do? is there any TI datasheets or application notes that can point me in the right direction?

  • 0 in reply to HSIN-CHE HSIEH
    TI__Mastermind 18051 points

    Sorry there are no applicatioin notes for this particular implmentation.